DNA barcoding identifies a species from the base sequence of a short, standard section of DNA, in the same way that a barcode identifies a product in a shop.A good barcode region varies very little within a species but a lot between species, and is present in all the organisms in a group. Different regions are used for different groups:
• animals: part of the mitochondrial gene COI (cytochrome c oxidase subunit I), about 650 base pairs long
• plants: two genes found in the chloroplast, rbcL and matK
• fungi: a non-coding region of ribosomal DNA called ITS.The method:
1. DNA is extracted from a small sample of tissue.
2. The barcode region is copied many times using PCR (the polymerase chain reaction).
3. The copied DNA is sequenced.
4. The sequence is compared with a reference database of barcodes from known species, such as the Barcode of Life Data System. The closest match identifies the species.DNA barcoding is useful because it:
• works on tiny, damaged or processed samples, such as hairs, eggs or meat products (for example to detect food fraud)
• identifies larvae and other stages that are hard to identify by appearance
• can reveal cryptic species that look identical
• can be used by non-experts.Its main limitation is that it only works if the species is already in the reference database, and very closely related species may have near-identical barcodes.
• animals: part of the mitochondrial gene COI (cytochrome c oxidase subunit I), about 650 base pairs long
• plants: two genes found in the chloroplast, rbcL and matK
• fungi: a non-coding region of ribosomal DNA called ITS.The method:
1. DNA is extracted from a small sample of tissue.
2. The barcode region is copied many times using PCR (the polymerase chain reaction).
3. The copied DNA is sequenced.
4. The sequence is compared with a reference database of barcodes from known species, such as the Barcode of Life Data System. The closest match identifies the species.DNA barcoding is useful because it:
• works on tiny, damaged or processed samples, such as hairs, eggs or meat products (for example to detect food fraud)
• identifies larvae and other stages that are hard to identify by appearance
• can reveal cryptic species that look identical
• can be used by non-experts.Its main limitation is that it only works if the species is already in the reference database, and very closely related species may have near-identical barcodes.